The present invention relates to a system for injecting fuel into compression ignition internal combustion engines.
Certain fuel injection systems for engines have been designed as unit injectors which incorporate hydraulically driven pressure intensifiers with a stepped plunger for injecting fuel into the engine""s cylinder, wherein the fuel delivery and timing are controlled by an electronically controlled valve. In addition, the spray pattern is controlled by means of modulating the base oil pressure supplied to the unit injector and/or by means of modulating the nozzle opening pressure.
The present invention concerns hydraulically actuated electronically controlled unit injection (HEUI) systems which are well known in the art. The most relevant art includes U.S. Pat. No. 5,785,021, the contents of which are incorporated herein by reference thereto.
U.S. Pat. No. 5,785,021 discloses a fuel injection system which comprises a pressure intensifier which is associated with hydraulically controlled differential valves. These valves comprise a poppet valve opening into a working chamber of the pressure intensifier. A throttling slot is provided between the poppet valve chamber and the working chamber, with either at least a bypass channel between the poppet valve chamber and a control chamber of the valve, or a bore connecting the working chamber to the control chamber of the valve.
Furthermore, International Application No. PCT/AU98/00073 discloses a fuel injection system in which a pressure intensifier is associated with a hydraulically controlled differential valve, which in turn defines a poppet opening into a working chamber of the pressure intensifier. The pressure intensifier comprises a plunger with an external groove for connection of a locking chamber of a nozzle with a compression chamber of the plunger during an injection cut-off position of the plunger, and for connection of the locking chamber to a control channel during other positions of the plunger. The pressure in the control channel is controlled by a hydraulic control system, which, in a preferred embodiment, is common for a set of injectors of the engine. In this manner, the injection system can be used for varying the shape of an injection curve and for providing a varying fuel injection pressure.
A primary object of the present invention is to provide an improved fuel injection system. In particular, it is an object of the present invention to provide improvements which increase the range of electronic control of an injection curve shape of the unit injector, improve the stability of fuel delivery in consecutive cycles of injections and between the unit injectors of a multi-cylinder engine, simplify the unit injector""s design, and improve the injection end quality.
These and other objects have now been realized by the invention of a fuel injector for use in an internal combustion engine comprising a fuel injector housing including an inlet port for the fuel, a spill port for release of the fuel, a working chamber, a piston disposed for reciprocal movement within the working chamber, a plunger attached to the piston, a nozzle for injecting the fuel into the internal combustion engine in response to the action of the plunger, a hydraulic valve movable between a closed position, an open position, and at least one intermediate position therebetween, the hydraulic valve including a first side and a second side, the first side of the hydraulic valve facing a control chamber and the second side of the hydraulic valve facing a poppet chamber, whereby the hydraulic valve moves between the control chamber and the poppet chamber, the hydraulic valve including a poppet defining the poppet chamber, the poppet including a first side and a second side, the first side of the poppet defining the poppet chamber and being in communication with the inlet port and the second side of the poppet being in communication with the working chamber, the poppet disposed with respect to the working chamber so as to provide a throttling slot between the working chamber and the poppet chamber, biasing means for urging the hydraulic valve towards the closed position in which the poppet chamber is not in communication with the inlet port, a control valve disposed between the control chamber and the spill port, and a primary bypass channel for connecting the poppet chamber to the control chamber, whereby during at least a portion of the initial movement of the hydraulic valve from the closed position to the open position the primary bypass channel is closed and when the hydraulic valve reaches the at least one intermediate position the primary bypass channel is open. In accordance with a preferred embodiment, the hydraulic valve includes a groove proximate to the first side of the hydraulic valve, whereby when the hydraulic valve is closed the groove opens the primary bypass channel, when the hydraulic valve is in the at least one intermediate position the first side of the hydraulic valve opens the primary bypass channel, and when the hydraulic valve is in a second intermediate position between the closed position and the at least one intermediate position the primary bypass channel is closed.
In accordance with one embodiment of the fuel injector of the present invention, the fuel injector includes a secondary bypass channel connecting the poppet chamber to the control chamber. In a preferred embodiment the fuel injector includes a secondary valve disposed is the secondary bypass channel for altering the flow area of the secondary bypass channel. Preferably, the fuel injector includes an engine management system for controlling the secondary valve.
In accordance with another embodiment of the fuel injector of the present invention, the fuel injector includes a tertiary bypass channel connecting the poppet chamber to the control chamber.
In accordance with another embodiment of the fuel injector of the present invention, the secondary valve cannot completely close the secondary bypass channel.
In accordance with another embodiment of the fuel injector of the present invention, the fuel injector includes a hydraulic control system for controlling the secondary valve. Preferably, the fuel injector includes an engine management system for controlling the hydraulic control system.
In accordance with another embodiment of the fuel injector of the present invention, the fuel injector includes a solenoid for actuating the secondary valve.
In accordance with the present invention, these objects have also been realized by the invention of a fuel injector for use in an internal combustion engine comprising a fuel injector housing including an inlet port for the fuel, a spill port for release of the fuel, a working chamber, a piston disposed for reciprocal movement within the working chamber, a compression chamber, a plunger attached to the piston and defining at least a portion of the compression chamber, a nozzle for injecting the fuel into the internal combustion engine in response to actuation by the plunger, a needle movable between a first position closing the nozzle and a second position opening the nozzle, a locking chamber, first biasing means disposed within the locking chamber for urging the needle into the first position, an outlet chamber connecting the nozzle to the compression chamber, a non-return valve for permitting the fuel to enter the compression chamber from the inlet port, a cut-off channel connecting the locking chamber to the compression chamber, a control channel for connecting the cut-off channel to the spill port, a secondary control valve for controlling the flow from the control channel to the spill port, a link channel connecting the control channel to either the inlet port or to a hydraulic control system of the internal combustion engine, the link channel and the secondary control valve being disposed such that when the secondary control valve is open, the pressure in the control channel is less than the pressure between the link channel and either the inlet port or the hydraulic control system of the internal combustion engine, the plunger being movable between a first position and at least one second position, whereby when the plunger is in the first position the cut-off channel is connected to the compression chamber and when the plunger is in the at least one second position the cut-off channel is connected to the control channel.
In accordance with a preferred embodiment of the fuel injector of the present invention, the fuel injector includes a hydraulic valve movable between a closed position, an open position, and at least one intermediate position therebetween, the hydraulic valve including a first side and a second side, the first side of the hydraulic valve facing a control chamber and the second side of the hydraulic valve facing a poppet chamber, whereby the hydraulic valve moves between the control chamber and the poppet chamber, the hydraulic valve including a poppet defining the poppet chamber, the poppet including a first side and a second side, the first side of the poppet defining the poppet chamber and being in communication with the inlet port and the second side of the poppet being in communication with the working chamber, the poppet disposed with respect to the working chamber so as to provide a throttling slit between the working chamber and the poppet chamber, second biasing means for urging the hydraulic valve towards the closed position in which the poppet chamber is not in communication with the inlet port, a control valve disposed between the control chamber and the spill port, and a primary bypass channel for connecting the poppet chamber to the control chamber, whereby during at least a portion of the initial movement of the hydraulic valve from the closed position to the open position the primary bypass channel is closed and when the hydraulic valve reaches the at least one intermediate position the primary bypass channel is open. In a preferred embodiment, the hydraulic valve includes a groove proximate to the first side of the hydraulic valve, whereby when the hydraulic valve is closed the groove opens the primary bypass channel, when the hydraulic valve is in the at least one intermediate position the first side of the hydraulic valve opens the primary bypass channel, and when the hydraulic valve is in a second intermediate position between the closed position and the at least one intermediate position the primary bypass channel is closed. Preferably, the fuel injector includes a secondary bypass channel connecting the poppet chamber to the control chamber. Most preferably, the fuel injector includes a secondary valve disposed is the secondary bypass channel for altering the flow area of the secondary bypass channel. In a preferred embodiment, the fuel injector includes an engine management system for controlling the secondary valve.
In accordance with one embodiment of the fuel injector of the present invention the fuel injector includes a tertiary bypass channel connecting the poppet chamber to the control chamber.
In accordance with another embodiment of the fuel injector of the present invention, the secondary valve cannot completely close the secondary bypass channel.
In accordance with another embodiment of the fuel injector of the present invention, the fuel injector includes a hydraulic control system for controlling the secondary valve. Preferably, the fuel injector includes an engine management system for controlling the hydraulic control system.
In accordance with another embodiment of the fuel injector of the present invention, the fuel injector includes a solenoid for actuating the secondary valve.
In accordance with another embodiment of the fuel injector of the present invention, the secondary valve includes a control chamber connected to the control channel, and the fuel injector includes third biasing means urging the secondary valve to close the secondary bypass channel, whereby increasing the pressure in the control chamber overcomes the third biasing means to open the additional bypass channel, and lowering the pressure in the control chamber permits the secondary valve to reduce the flow in the secondary bypass channel. Preferably, the control valve and the secondary control valve comprise solenoid valves.
In accordance with one embodiment of the fuel injector of the present invention, the first biasing means has a variable stiffness.
In accordance with one embodiment of the present invention there is provided a fuel injection system for an internal combustion engine with a fuel injector, the injector comprising an inlet port; a spill port; a pressure intensifier comprising a piston forming a working chamber and a plunger adapted for injecting fuel through a nozzle; an hydraulic valve comprising a control chamber and a poppet chamber and having a poppet located between the inlet port and the working chamber and opening into the working chamber, wherein the poppet provides a throttling slot; means for biasing the hydraulic valve towards its closed position; a control valve installed between the control chamber and the spill port; a bypass channel for connection of the poppet chamber to the control chamber; and wherein the hydraulic valve is adapted to control the flow area of the bypass channel such that the bypass channel is open when the hydraulic valve is in its closed and open positions, or near these positions, and is closed during the other positions of the hydraulic valve.
In a preferred embodiment of the present invention, there is also a third bypass channel connecting the poppet and control chambers, such that when the additional bypass channel is closed by the secondary control valve, the third bypass channel defines the opening rate of the hydraulic valve during the positions of the hydraulic valve when it keeps the bypass channel closed.
In accordance with another embodiment of the present invention there is provided a fuel injection system for an internal combustion engine with a fuel injector, the injector comprising an inlet port; a spill port; a pressure intensifier comprising a piston forming a working chamber and a spill chamber and a plunger forming a compression chamber, wherein the working chamber is adapted to be connected either to the inlet port or to the spill port according to the commands from an engine management system in order to enable the pressure intensifier to perform injections; a nozzle with a needle, a locking chamber, means biasing the needle to close the nozzle and an outlet chamber connected to the compression chamber; a non-return valve, the inlet of the non-return valve being connected to the inlet port and the outlet of the non-return valve being connected to the compression chamber; a cut-off channel connected to the nozzle locking chamber; a control channel; an additional control valve installed between the control channel and the spill port; a link channel connecting the control channel to the inlet port; and in which the flow areas of the link channel and the additional control valve are such that when the additional control valve is open the pressure in the control channel becomes less than the pressure upstream of the link channel; the plunger being adapted to connect the cut-off channel to the compression chamber at an injection cut-off position of the plunger, and adapted to connect the cut-off channel to the control channel at other positions of the plunger.
The differences between the injector and injection system of an aspect of the present invention and that of the specifications mentioned above reside firstly in the inclusion of an additional bypass channel, connecting the poppet chamber to a control chamber, and a secondary valve which is adapted to control the flow area of the additional bypass channel in accordance with a pressure level in an hydraulic control system or in a control channel, where an hydraulic valve is adapted to control the flow area of a bypass channel for connection of the poppet chamber to the control chamber; secondly, the hydraulic valve controls the flow area of the bypass channel such that the bypass channel is open when the hydraulic valve is in its closed and open positions, or near these positions, and closed during the other positions of the hydraulic valve (HDV). By controlling the pressure in the hydraulic control system or in the control channel, the secondary valve can be controlled to open or close the additional bypass channel. When such pressure is increased, the secondary valve opens the additional bypass channel, and vice versa. As the opening speed of the hydraulic valve is dependent upon the flow area of the bypass channels, it is possible to control the opening speed of the hydraulic valve during its initial opening by controlling the position of the secondary valve and the flow area of the bypass channel. Slower hydraulic valve opening delays the injection pressure build-up. During the final part of the opening of the hydraulic valve the bypass channel is open and therefore the pressure in the control chamber is increased, which helps to fully open the hydraulic valve and reduce its hydraulic restriction.
It is preferable to use an hydraulic control system that is common for a set of injectors on an engine to control the positions of the secondary valves. The pressure in this common hydraulic control system is controlled by an engine management system. This helps to ensure uniform injection patterns throughout the engine cylinders, to simplify the injection system design and help keep the cost down as in this case only one pressure regulator is required and it can be mounted anywhere on an engine. Alternatively, the hydraulic control system can be replaced by a direct solenoid control of the secondary valves, which can be executed by a single solenoid and a mechanical arrangement transmitting the solenoid action to all of the injectors of an engine.
Another embodiment of the present invention resides in the provision of a link channel between a control channel and an inlet port, or between the control channel and an hydraulic control system, and in the provision of an additional control valve between the control channel and a spill port, in which a plunger is adapted to disconnect the control channel from a cut-off channel during a cut-off position of the plunger, and further where the flow areas of the additional control valve and the link channel are such that when the additional control valve is open the pressure in the control channel becomes less than the pressure in the hydraulic control system or in the inlet port. The pressure in the hydraulic control system is typically controlled by an engine management system. Thus, during a position of the plunger other than the cut-off position, a pilot or a boot injection is possible by means of opening the additional control valve. During the cut-off position of the plunger the control channel is disconnected from the cut-off channel, and the additional control valve is thus not subjected to a high pressure, and the volume of the cut-off channel is kept to a minimum.
Different embodiments of the present invention enable a wider range of control of the injection curve shape independently of the common rail (actuating) pressure, simplification of the unit injector design, and an improvement in the injection end quality and injector reliability.